/*
 * Copyright 1999-2018 Alibaba Group Holding Ltd.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.alibaba.nacos.common.utils;

/**
 * @author <a href="mailto:liaochuntao@live.com">liaochuntao</a>
 */
public interface Observer {

	/**
	 * This method is called whenever the observed object is changed. An
	 * application calls an {@code Observable} object's
	 * {@code notifyObservers} method to have all the object's
	 * observers notified of the change.
	 *
	 * @param   o     the observable object.
	 * @param   arg   an argument passed to the {@code notifyObservers}
	 *                 method.
	 */
	void update(Observable o, Object arg);

}
